Had a Pine64 running Ubuntu for 6 months without probs. After a reboot, the device did not start. Have a second pine so was able to mix and match things and determine that the SD card was the issue. The original Pine boots with a new SD card.

The 'bad' SD card mounts and is perfectly readable on Linux or Windows desktop system. Tried to format a new SD card and copy the contents from the bad SD card but no joy.

I understand that not all SD cards are high quality, and also that shit can happen ... so, the question is - how can we backup the SD card so we can recover from a bad SD card?